Gate valve

ABSTRACT

A gate valve has a transfer chamber-side valve element and a process chamber-side valve element connected to a single shaft. A rotary latch pivotably supported on an inner surface of one of the valve element with the rotary latch having a latch surface at a forward end thereof, wherein when a rotational force is applied to the rotary latch in one direction, the latch surface is pressed against a joint surface of the single shaft, whereby the valve element is latched to said single shaft, and when a rotational force is applied to the rotary latch in the opposite direction, the latch surface is separated from the joint surface of the single shaft to unlatch the valve element.

This application is a divisional of U.S. application Ser. No. 10/738,678filed Dec. 16, 2003, now U.S. Pat. No. 7,066,443 which claims priorityto Japanese Patent Application No. 2002-363682 filed Dec. 16, 2002.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a gate valve provided between vacuumchambers in a semiconductor manufacturing system, etc., e.g. between aprocess chamber (hereinafter referred to as “PC”) and a transfer chamber(hereinafter referred to as “TC”).

2. Description of the Related Art

A patent document 1 (U.S. Pat. No. 6,390,448) discloses a gate valvewherein mutually opposing walls of the gate valve body are formed with aPC (process chamber) opening and a TC (transfer chamber) opening,respectively, and the PC opening and the TC opening are selectivelyclosed with a double-sided valve member having a PC-side valve elementand a TC-side valve element. With the disclosed technique, for example,the TC opening is closed to keep the transfer chamber at a vacuum whilethe process chamber is opened to the atmosphere, thereby making itpossible to carry out repairs in the process chamber while using thetransfer chamber at a vacuum. Moreover, it is possible to replace theseal of the PC-side valve element in a state where the TC-side openingis closed with the TC-side valve element. It is also possible to preventfragments, contaminants, etc. in the process chamber from entering thetransfer chamber. Thus, it is possible to continue an operation in onevacuum chamber during the repair of the other vacuum chamber or duringthe repair of the valve element in the other vacuum chamber.

The gate valve in the patent document 1 tilts a single shaft at an upperposition to allow the double-sided valve member to selectively close thePC opening and the TC opening and to place the double-sided valve memberin an intermediate position between the two openings. When the singleshaft is moved to a lower position, the two openings are fully open,thereby allowing a workpiece to pass therethrough. To perform theseoperations, the single shaft is secured to the double-sided valvemember, and the single shaft is moved with three air cylinders. However,the use of three air cylinders causes an increase in size of the gatevalve and also a rise in cost. Meanwhile, it is possible to clean theseal surfaces of the two walls of the valve body by removing the topcover from the valve body. However, it is impossible to replace theseals of the double-sided valve member. In addition, a space forcleaning is provided between each valve element and the associated wall,and the valve elements are coupled by using hinge pins. Thus, thespacing between the valve elements is large, and hence the longitudinalwidth of the valve body is unfavorably large.

SUMMARY OF THE INVENTION

A first object of the present invention is to provide a gate valvehaving a transfer chamber-side valve element and a process chamber-sidevalve element, wherein a single shaft is actuated with a singlethree-position air cylinder to selectively close a process chamberopening and a transfer chamber opening or fully open both the processchamber opening and the transfer chamber opening to allow an object topass therethrough.

A second object of the present invention is to enable replacement of theseal of the process chamber- or transfer chamber-side valve element thatis not closed when the process chamber opening or the transfer chamberopening is selectively closed.

To attain the above-described objects, the present invention is appliedto a gate valve including a valve body having a transfer chamber openingand a process chamber opening formed in mutually opposing walls thereof,respectively. A transfer chamber-side valve element and a processchamber-side valve element that are connected to a single shaft aredisposed in the valve body. The transfer chamber-side valve element andthe process chamber-side valve element are controlled by actuation ofthe single shaft so that the transfer chamber-side valve element closesthe transfer chamber opening, or the process chamber-side valve elementcloses the process chamber opening, or both the transfer chamber-sidevalve element and the process chamber-side valve element fully open thetransfer chamber opening and the process chamber opening, respectively,to allow an object to pass therethrough.

According to a first arrangement of the present invention, a levermember is secured to the single shaft of the above-described gate valve,and a roller is supported by the lever member. The roller is kept inengagement with a cam groove of a cam member. The cam groove has aposition A, a position B, and a position C. A cam support member forsupporting the cam member is connected to a piston rod of athree-position air cylinder. The piston rod has a first position, asecond position, and a third position. A spring is interposed betweenthe lever member and the cam support member. When the piston rod is inthe first position, the transfer chamber-side valve element and theprocess chamber-side valve element fully open the transfer chamberopening and the process chamber opening, respectively. As the piston rodshifts from the first position to the second position, the roller shiftsfrom engagement with the position A of the cam groove to engagement withthe position B. This shift causes the process chamber-side valve elementto close the process chamber opening (in a state where the transferchamber-side valve element opens the transfer chamber opening). As thepiston rod shifts from the second position to the third position, theroller shifts from the engagement with the position B of the cam grooveto engagement with the position C. This shift causes the transferchamber-side valve element to close the transfer chamber opening (whilethe process chamber-side valve element opens the process chamberopening). It should be noted that two rollers may be supported on bothlateral sides of the lever member and engaged in respective cam groovesof two cam members.

According to a second arrangement of the present invention, a pivot isconnected to the lever member in the first arrangement, and apivot-receiving groove is provided on the lower side of the valve body.When the roller shifts from the engagement with the position A of thecam groove to the engagement with the position B, and also when theroller shifts from the engagement with the position B of the cam grooveto the engagement with the position C, the pivot engages with thepivot-receiving groove to serve as a supporting point for the shiftingof the roller. The arrangement may be such that two pivots are connectedto both lateral sides of the cam member, and two pivot-receiving groovesare provided on the lower side of the valve body.

According to a third arrangement of the present invention, a groovedplate is connected to the cam member in the first or second arrangement,and a bolt is threaded into the lever member. The shank of the bolt ispositioned in a yoke groove of the grooved plate.

In addition, the present invention is applied to a gate valve includinga valve body having a transfer chamber opening and a process chamberopening formed in mutually opposing walls thereof, respectively. Atransfer chamber-side valve element and a process chamber-side valveelement that are connected to a single shaft are disposed in the valvebody. The transfer chamber-side valve element and the processchamber-side valve element are controlled by actuation of the singleshaft so that the transfer chamber-side valve element closes thetransfer chamber opening, or the process chamber-side valve elementcloses the process chamber opening, or both the transfer chamber-sidevalve element and the process chamber-side valve element fully open thetransfer chamber opening and the process chamber opening, respectively,to allow an object to pass therethrough.

According to a fourth arrangement of the present invention, a rotarylatch is pivotably supported on the inner surface of at least one of theprocess chamber-side valve element and the transfer chamber-side valveelement of the above-described gate valve. The rotary latch has a latchsurface at a forward end thereof. When a rotational force is applied tothe rotary latch in one direction, the latch surface is pressed againsta joint surface of the single shaft, whereby the at least one of theprocess chamber-side valve element and the transfer chamber-side valveelement is latched to the single shaft. When a rotational force isapplied to the rotary latch in a direction opposite to the onedirection, the latch surface is separated from the joint surface of thesingle shaft to unlatch the at least one of the process chamber-sidevalve element and the transfer chamber-side valve element.

According to a fifth arrangement of the present invention, a rod supportmember is provided on the inner surface of the at least one of theprocess chamber-side valve element and the transfer chamber-side valveelement in the fourth arrangement at a position above the rotary latch.The rod support member has an internal thread. A spring is interposedbetween the rod support member and a rear end portion of the rotarylatch. The gate valve further includes a maintenance rod having anexternal thread. The external thread of the maintenance rod is engagedwith the internal thread of the rod support member. A rotational forceis applied to the rotary latch in the one direction by resilient forceof the spring. A rotational force is applied to the rotary latch in thedirection opposite to the one direction by advance of the distal end ofthe external thread of the maintenance rod.

According to a sixth arrangement of the present invention, the latchsurface of the rotary latch and the joint surface of the single shaft inthe fourth or fifth arrangement are slant surfaces as seen in atop-view. The whole of the slant latch surface is joinable to the slantjoint surface.

According to a seventh arrangement of the present invention, a shaftretaining member is formed on the inner surface of the at least one ofthe process chamber-side valve element and the transfer chamber-sidevalve element in any of the fourth to sixth arrangements. The shaftretaining member has a retaining surface formed at a distal end thereof.A second joint surface is formed on a side of the single shaft laterallyopposite to the joint surface. The retaining surface of the shaftretaining member and the second joint surface of the single shaft areslant surfaces as seen in a top view. The whole of the slant retainingsurface is joinable to the slant second joint surface.

According to an eighth arrangement of the present invention, a rodsupport member is provided above the rotary latch in the fourtharrangement. A latch screw is provided on the rod support member at aposition above one of forward and rear end portions of the rotary latch.An unlatch screw is provided on the rod support member at a positionabove the other of the forward and rear end portions of the rotarylatch. A rotational force is applied to the rotary latch in onedirection by advance of the latch screw and retraction of the unlatchscrew. A rotational force is applied to the rotary latch in a directionopposite to the one direction by retraction of the latch screw andadvance of the unlatch screw.

According to a ninth arrangement of the present invention, the rodsupport member in the eighth arrangement is formed with two pairs ofinsertion holes and internal threads that are vertically adjacent toeach other, respectively. The latch screw is engaged with one of theinternal threads. The unlatch screw is engaged with the other of theinternal threads. The latch screw and the unlatch screw have respectivegrooves. (e.g. cone hexagon sockets) for engagement formed on theirheads. The latch screw and the unlatch screw are rotatable with a toolby engaging its tip with the groove of each screw. It should be notedthat the inner diameter of the each insertion hole may be smaller thanthe outer diameter of the associated screw.

According to a tenth arrangement of the present invention, the latchsurface of the rotary latch and the joint surface of the single shaft inthe eighth or ninth arrangement are slant surfaces as seen in a topview. The whole of the slant latch surface is joinable to the slantjoint surface.

According to an eleventh arrangement of the present invention, a shaftretaining member is formed on the inner surface of the at least one ofthe process chamber-side valve element and the transfer chamber-sidevalve element in any of the eighth to tenth arrangements. The shaftretaining member has a retaining surface formed at a distal end thereof.A second joint surface is formed on a side of the single shaft laterallyopposite to the joint surface. The retaining surface of the shaftretaining member and the second joint surface of the single shaft areslant surfaces as seen in a top view. The whole of the slant retainingsurface is joinable to the slant second joint surface.

The gate valve according to any of the first to third arrangements has atransfer chamber-side valve element and a process chamber-side valveelement and enables a process chamber opening and a transfer chamberopening to be selectively closed or fully opened to allow an object topass therethrough by using a single three-position air cylinder.Therefore, the gate valve according to the present invention requiresonly one actuator and hence provides the following advantages {circlearound (1)} and {circle around (2)} over the gate valve disclosed in thepatent document 1:

{circle around (1)} The number of component parts reduces, andreliability improves. In addition, costs reduce, and the length andbreadth of the control body reduce.

{circle around (2)} Signal and position detecting systems become simple.Therefore, reliability improves, and there will be no failure of thevalve elements due to an error signal.

The gate valve according to any of the fourth to eleventh arrangementsallows replacement of the seal of the process chamber- or transferchamber-side valve element (at least one of these valve elements) thatis not closed when the process chamber opening or the transfer chamberopening is selectively closed, by removing the valve element from thevalve body. Therefore, the gate valve according to the present inventionprovides the following advantages (1) to (4) over the gate valvedisclosed in the patent document 1:

(1) The gate valve according to the present invention uses the rotarylatch and the shaft retaining member, which are thin in thickness, asmeans for securing the valve element to the single shaft. Therefore,there is no need of space for bolting and unbolting. Consequently, thespacing between the process chamber-side valve element and the transferchamber-side valve element can be minimized. Thus, because the spacingbetween the process chamber-side seat surface and the transferchamber-side seat surface can be reduced, the longitudinal width of thevalve body can be minimized. In contrast to this, the gate valve of thepatent document 1 has a large spacing between the two valve elements.The spacing between each valve element and the associated wall is alsolarge. Accordingly, the longitudinal width of the valve body isunfavorably large.

(2) Attachment and detachment of the valve element can be done byactuating the maintenance rod partly inserted into the valve body. It isunnecessary for an operator to insert his/her hand into the valve bodyas in the case of bolting and unbolting the valve element. Therefore,there is no possibility that the interior of the valve body will becontaminated.

(3) To remove and replace the valve element, the latch is undone simplyby threading the maintenance rod into the rod support member by hand orby retracting the latch screw and advancing the unlatch screw, and thenthe maintenance rod or the like is pulled up. By doing so, the valveelement can be removed. A new valve element can be installed byreversing the procedure for removal. Therefore, the replacing operationcan be facilitated and performed in a shortened period of time. Thus,the downtime of the system can be reduced to a considerable extent.

(4) Even if the gate valve operates accidentally during replacement ofthe valve element, there is no danger of the operator's hand beingcaught between the valve element and the seat surface.

The invention accordingly comprises the features of construction,combinations of elements, and arrangement of parts which will beexemplified in the construction hereinafter set forth, and the scope ofthe invention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a partly-sectioned front view of an embodiment of the gatevalve according to the present invention (in a first position).

FIG. 1B is a sectional side view of the embodiment taken along the lineI—I in FIG. 1A.

FIG. 2A is a sectional side view of the embodiment in a state where apiston rod is in an intermediate position.

FIG. 2B is a sectional side view of the embodiment in a state where thepiston rod is in a second position.

FIG. 2C is a sectional side view of the embodiment in a state where thepiston rod is in a third position.

FIG. 3 is an enlarged view of an essential part of FIG. 1A.

FIGS. 4A to 4C are views showing a first example of an arrangement forremoving a process chamber- or transfer chamber-side valve element thatis not closed when a process chamber opening or a transfer chamberopening is selectively closed, of which: FIG. 4A is a plan view showingthe arrangement in a state where a bonnet is detached; FIG. 4B is asectional view taken along the line II—II in FIG. 4C; and FIG. 4C is asectional side view taken along the line III—III in FIG. 4A, showing alatched state.

FIG. 5A is an enlarged view of an essential part of FIG. 4B.

FIG. 5B is an enlarged view of an essential part of FIG. 4C.

FIG. 6A is an enlarged view corresponding to FIG. 5A, showing anunlatched state.

FIG. 6B is an enlarged view corresponding to FIG. 5B, showing anunlatched state.

FIGS. 7A to 7C are views showing a second example of an arrangement forremoving a process chamber- or transfer chamber-side valve element thatis not closed when a process chamber opening or a transfer chamberopening is selectively closed, of which: FIG. 7A is a sectional viewtaken along the line IV—IV in FIG. 7B; FIG. 7B is a sectional side viewtaken along the line V—V in FIG. 7A, showing a latched state; and FIG.7C is a sectional side view corresponding to FIG. 7B, showing anunlatched state.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1A to 7C show embodiments of the gate valve according to thepresent invention. FIG. 1A to 3 show a structure for vertically movingand tilting a single shaft 15. As shown in FIGS. 1A and 1B, a gate valvehas a valve body 10 comprising a front wall 11, a rear wall 12, a leftwall 18, a right wall 19, and a bottom wall 20. A bonnet (cover) 22 issecured to the upper side of the valve body 10. A control body 27 isconnected to the lower side of the valve body 10. The gate valve has aTC (transfer chamber) opening 13 in the front wall 11 of the valve body10 and a PC (process chamber) opening 14 in the rear wall 12. A TC-sidevalve element 25 and a PC-side valve element 26 are connected to anupper portion 15A of a single shaft 15. The TC-side valve element 25 andthe PC-side valve element 26 are disposed in the valve body 10. Theupper portion 15A of the single shaft 15 is inserted into an insertionhole 21 in the bottom wall 20. The single shaft 15 extends into thecontrol body 27. In response to the actuation of the single shaft 15, aseal 63 of the TC-side valve element 25 presses against a TC-side sealsurface 23 to close the TC opening 13, or a seal 64 of the PC-side valveelement 26 presses against a PC-side seal surface 24 to close the PCopening 14, or the TC-side valve element 25 and the PC-side valveelement 26 are moved downward to fully open both the openings 13 and 14,thereby allowing an object (workpiece) to pass therethrough.

A lever member 30 is secured to the single shaft 15. Two rollers 31A and31B are supported on both sides of the lower end of the lever member 30.The rollers 31A and 31B are kept in engagement with respective camgrooves 33A and 33B of two cam members 32A and 32B. The cam members 32Aand 32B are supported by a cam support member 34. Both end portions ofthe cam support member 34 are connected to respective piston rods 36Aand 36B of three-position air cylinders 35A and 35B. A spring 37 isinterposed between the lever member 30 and the cam support member 34.The TC opening 13 is communicated with a TC (transfer chamber) through apassage (not shown). The PC opening 14 is communicated with a PC(process chamber) through a passage (not shown).

The single shaft 15 has, in order from the upper side thereof, an upperportion 15A, an enlarged portion 15B, a lower portion 15C, and anexternal thread 15D. A stepped insertion bore 28 in the lever member 30has an upper large-diameter portion 28A, an intermediate-diameterportion 28B, and a lower large-diameter portion 28C. The lower portion15C of the single shaft 15 is inserted in the intermediate-diameterportion 28B of the stepped insertion bore 28. A nut 38 is engaged withthe external thread 15D of the single shaft 15. The lower end of theenlarged portion 15B of the single shaft 15 is in contact with a stepportion of the upper large-diameter portion 28A of the stepped insertionbore 28. The upper end of a bellows 39 is sealingly secured to theperiphery of the insertion hole 21 in the bottom of the valve body 10.The lower end of the bellows 39 is sealingly secured to the outerperipheral surface of the lower end of the enlarged portion 15B of thesingle shaft 15.

The two three-position air cylinders 35A and 35B are secured torespective upper positions in the left and right end portions of thecontrol body 27. External threads on the distal ends of the two pistonrods 36A and 36B of the air cylinders 35A and 35B are inserted intorespective insertion holes 40 provided in the left and right endportions of the cam support member 34. Nuts 41 are engaged with theexternal threads to secure the piston rods 36A and 36B to the camsupport member 34. Grooved plates 42A and 42B are connected to therespective upper ends of the cam members 32A and 32B. Bolts 44A and 44Bare threaded into both sides of the lever member 30. The shanks of thebolts 44A and 44B are positioned in respective yoke grooves 43 of thegrooved plates 42A and 42B. Pivots (rollers) 45A and 45B are connectedto both sides of the upper end portion of the lever member 30.Pivot-receiving grooves 46A and 46B are provided on the lower side ofthe valve body 10. When moved upward, the pivots 45A and 45B engage withthe pivot-receiving grooves 46A and 46B, respectively.

The three-position air cylinders 35A and 35B each have a cylinder tube48. An annular collar 49 is formed at an upper position on the innerwall of the cylinder tube 48. A stop piston 50 is slidably disposed inthe cylinder tube 48 above the annular collar 49. The lower side of thestop piston 50 is formed with a stopper 51 projecting downward. Anapproximately cylindrical recirculating linear ball bearing 52 ishermetically disposed at a lower position inside the cylinder tube 48. Aflange 53 is formed at the upper end of the recirculating linear ballbearing 52. A piston 54 is slidably disposed in the cylinder tube 48 soas to be movable between the flange 53 and the annular collar 49. Thepiston rod 36A (36B) of the piston 54 is slidably and hermeticallysupported by a center hole of the flange 53. The piston rod 36A isreciprocatably supported by the recirculating linear ball bearing 52.Thus, a load acting perpendicularly on the piston rod 36A is borne.

A first cylinder chamber 55 is formed between the flange 53 and thepiston 54 in each of the three-position air cylinders 35A and 35B. Asecond cylinder chamber 56 is formed between the piston 54 and the stoppiston 50. A third cylinder chamber 57 is formed between the stop piston50 and an upper end plate. A side wall of the control body 27 has, inorder from the upper side thereof, a stopper port 58, an open port 59and a close port 60. These ports are formed in an open state. Thestopper port 58, the open port 59 and the close port 60 are respectivelycommunicated with the upper part of the third cylinder chamber 57, theupper part of the second cylinder chamber 56 and the lower part of thefirst cylinder chamber 55 of each of the three-position air cylinders35A and 35B through respective passages (not shown).

Next, the operation of the single shaft 15 will be described. The pistonrods 36A and 36B each have three positions, i.e. a first position, asecond position, and a third position. When the stopper port 58 and theopen port 59 are communicated with a compressed air pressure sourcewhile the close port 60 is communicated with the atmosphere, the pistonrods 36A and 36B are placed in a first position (lower extremityposition) shown in FIG. 1. When the piston rods 36A and 36B are in thefirst position, the TC-side valve element 25 and the PC-side valveelement 26 are placed in a fully open position. At this time, aworkpiece can freely pass through the TC opening 13 and the PC opening14. Thus, loading and unloading of the workpiece into and from theprocess chamber are performed. As shown in FIG. 1B, the cam groove 33A(33B) is in the shape of “>” and has three positions, i.e. position A(upper end position), position B (intermediate position), and position C(lower end position), in order from the upper side thereof. The positionA (upper end position) is located in the lateral center of the camgroove 33A (33B). The position B (intermediate position) is locatedrightward of the lateral center. The position C (lower end position) islocated leftward of the lateral center. In the first position, therollers 31A and 31B are engaged with the respective upper end positionsof the cam grooves 33A and 33B. Meanwhile, the yoke grooves 43 are inthe shape of a combination of a triangle and a rectangle connected inseries vertically. Each yoke groove 43 has a recess at the upper endthereof. The recess has a size just large enough for the shank of thebolt 44A (44B) to engage therein. In the first position, the shanks ofthe bolts 44A and 44B are located at the respective upper end positions(recesses) in the yoke grooves 43A and 43B of the grooved plates 42A and42B.

Next, when the close port 60 and the stopper port 58 are communicatedwith the compressed air pressure source while the open port 59 iscommunicated with the atmosphere, each piston 54 begins to move upward,and the piston rods 36A and 36B, which are connected to the respectivepistons 54, together with the cam support member 34 and the cam members32A and 32B, move upward simultaneously with the pistons 54. The upwardmovement of the cam support member 34 is transmitted to the lever member30 through the spring 37. Consequently, the single shaft 15, which isconnected to the lever member 30, together with the TC-side valveelement 25 and the PC-side valve element 26, moves upward simultaneouslywith the lever member 30. When the pivots 45A and 45B engage in therespective pivot-receiving grooves 46A and 46B as a result of the upwardmovement of the lever member 30, the lever member 30 stops movingupward, thus reaching an intermediate position (between the firstposition and the second position) shown in FIG. 2A. The TC-side valveelement 25 and the PC-side valve element 26 half open the TC opening 13and the PC opening 14, respectively. In this position, a fluid can passthrough the TC opening 13 and the PC opening 14, but a workpiece cannotpass therethrough. In the intermediate position, the rollers 31A and 31Bremain engaged in the positions A of the cam grooves 33A and 33B, andthe shanks of the bolts 44A and 44B remain located at the upper endpositions in the yoke grooves 43A and 43B of the grooved plates 42A and42B.

Despite the termination of the upward movement of the lever member 30 inthe intermediate position, the cam members 32A and 32B continue movingupward, causing the spring 37 to be compressed. Thus, the roller 31A(31B) is pushed by a first cam 61 (see FIG. 2A) at the left side of thecam groove 33A (33B). As a result, the roller 31A (31B) shifts from theengagement with the position A to the engagement with the position B.Consequently, the single shaft 15 and the lever member 30 begin to pivotcounterclockwise (left-handed direction) as viewed in FIGS. 2A and 2Babout the pivots 45A and 45B. When the piston 54 abuts on the stopper 51in the lowered position, the upward movement of the piston 54 stops.Thus, the piston rods 36A and 36B reach the second position shown inFIG. 2B. It should be noted that the pressure-receiving area at theupper side of the stop piston 50 is larger than the pressure-receivingarea at the lower side of the piston 54. Therefore, the stop piston 50can stop the upward movement of the piston 54. To make the stoppingoperation even more reliable, however, the diameter of the thirdcylinder chamber 57 and the diameter of the stop piston 50 may befurther increased. In response to the shift of the piston rods 36A and36B from the intermediate position to the second position, the rollers31A and 31B shift from the engagement with the position A to engagementwith the position B. As a result of the shifting of the rollers 31A and31B, the PC-side valve element 26 closes the PC opening 14. In thissecond position, a semiconductor workpiece is processed in the processchamber. It should be noted that in the second position shown in FIG.2B, the shank of the bolt 44A is at a position closer to the upper endof the yoke groove 43 and rightward of the lateral center of the yokegroove 43.

Usually, after the semiconductor workpiece has been processed in thesecond position, the piston 54 is returned to the first position tounload the processed semiconductor workpiece. Then, a workpiece to beprocessed is loaded, and the piston 54 is moved to the second position.However, when the process chamber needs repairs or it is desired toreplace the seal 64 of the PC-side valve element 26, the close port 60is communicated with the compressed air pressure source while the openport 59 and the stopper port 58 are communicated with the atmosphere.Consequently, the piston 54 further moves upward, pushing up the stopper51, and the piston rods 36A and 36B move from the second position inFIG. 2B to the third position (upper extremity position) shown in FIG.2C. In response to the shift of the piston rods 36A and 36B from thesecond position to the third position, the rollers 31A and 31B shiftfrom the engagement with the position B to engagement with the positionC. In the process of this shift, a second cam 62 (see FIG. 2A) pushesthe roller 31A (31B), causing the single shaft 15 and the lever member30 to begin pivoting clockwise (right-handed direction) as viewed inFIGS. 2B and 2C about the pivots 45A and 45B. This pivoting motioncauses the PC-side valve element 26 to move to a half-open position.Thus, the PC opening 14 is half opened. At the same time, the pivotingmotion causes the TC-side valve element 25 to close the TC opening 13.It should be noted that in the third position shown in FIG. 2C, theshank of the bolt 44A is at a position closer to the lower end of theyoke groove 43 and leftward of the lateral center of the yoke groove 43.

The following is a description of a first example of an arrangement forremoving the PC- or TC-side valve element that is not closed when the PCopening 14 or the TC opening 13 is selectively closed, to replace theseal of the valve element, and for reinstalling the valve element afterthe replacement. The description will be made with reference to FIGS. 4Ato 6B. A rotary latch 66 is rotatably supported on the inner surface ofat least one of the PC-side valve element 26 and the TC-side valveelement 25 (i.e. at least one of the mutually opposing surfaces of thevalve element 25 and 26 in FIGS. 4A and 4B). The rotary latch 66 has alatch surface 67 formed at a forward end thereof (right end in FIG. 5A).The following arrangement is common to the first example and a secondexample described later. That is, when a rotational force is applied tothe rotary latch 66 in one direction, the latch surface 67 is pressedagainst a joint surface 73 of the single shaft (upper portion) 15A.Thus, the valve element is latched to the single shaft 15A. When arotational force is applied to the rotary latch 66 in a directionopposite to the one direction, the latch surface 67 is separated fromthe joint surface 73 of the single shaft 15A to unlatch the valveelement. In the first example, the rotary latch 66 is pivoted in onedirection by resilient force of a spring 68. Thus, the rotary latch 66is urged to press the latch surface 67 against the joint surface 73 ofthe single shaft 15A, thereby allowing the valve element to be latchedto a predetermined position. A rod support member 77 is provided on theinner surface of the valve element. The rod support member 77 has aninternal thread 78A extending therethrough vertically. An externalthread 83A of a maintenance rod (rod for attachment and detachment) 82Ais engaged with the internal thread 78A. The rotary latch 66 is pivotedin a direction opposite to the one direction by the advance of thedistal end 84A of the external thread 83A of the maintenance rod 82A. Asa result, the latch surface 67 is separated from the joint surface 73,and hence the valve element is unlatched.

In FIGS. 4A to 6B, both the PC-side valve element 26 and the TC-sidevalve element 25 are provided with the arrangement for replacing seals.The following description is, however, centered on the arrangementprovided for the PC-side valve element 26. FIGS. 5A to 5B show thePC-side valve element 26 in the latched state. The bonnet 22 has beenremoved from the top of the valve body 10. The rod support member 77 isprovided on the inner surface of the PC-side valve element 26 at aposition where the upper end surface of the rod support member 77 andthe upper end surface of the PC-side valve element 26 are coincidentwith each other. The rod support member 77 may be integrated with thePC-side valve element 26. Alternatively, the rod support member 77 maybe prepared as a member separate from the PC-side valve element 26 andsecured to the latter with bolts, nuts, etc. The upper end of the singleshaft 15A is positioned in close proximity to the lower side of the rodsupport member 77. The rotary latch 66 is disposed at the left side ofthe single shaft 15A at a position below and somewhat away from the rodsupport member 77. At the right side of the single shaft 15A, a shaftretaining member 90 is provided on the PC-side valve element 26 at aposition below and away from the rod support member 77.

The rotary latch 66 has a stepped insertion hole 69 at an upper andapproximately central position in the lateral direction thereof. Arotating shaft 70 is inserted in the stepped insertion hole 69. ThePC-side valve element 26 has an internal thread 71 formed in the innerside thereof. An external thread formed on the distal end of therotating shaft 70 is engaged with the internal thread 71. The rotarylatch 66 has a lower spring seat 72 formed on the rear end portion (leftend portion in FIG. 5B) thereof. The upper end of the lower spring seat72 is open. The rod support member 77 has an upper spring seat 79 formedon the lower and left end portion thereof. The spring 68 is interposedbetween the lower spring seat 72 and the upper spring seat 79. Therotary latch 66 is urged in the counterclockwise direction (onedirection) by the resilient force of the spring 68. As seen in a topview, e.g. FIG. 5A, the latch surface 67 of the rotary latch 66 and thejoint surface 73 of the single shaft 15A are slant surfaces. The wholeof the slant latch surface 67 is joinable to the slant joint surface 73.

The shaft retaining member 90 is formed on the inner surface of thePC-side valve element 26. The shaft retaining member 90 may be integralwith the PC-side valve element 26 as shown in the drawings.Alternatively, the shaft retaining member 90 may be prepared as a memberseparate from the PC-side valve element 26 and secured to the latterwith bolts, nuts, etc. The shaft retaining member 90 has a retainingsurface 91 at the distal end thereof. A second joint surface 74 isformed on a side of the single shaft 15A laterally opposite to the jointsurface 73. As seen in a top view, e.g. FIG. 5A, the retaining surface91 of the shaft retaining member 90 and the second joint surface 74 ofthe single shaft 15A are slant surfaces. The whole of the slantretaining surface 91 is joinable to the second joint surface 74. In thelatched state shown in FIGS. 4A to 5B, the whole latch surface 67presses the joint surface 73 with the resilient force of the spring 68.Counterforce produced at this time is transmitted to the retainingsurface 91 through the rotary latch 66, the rotating shaft 70, thePC-side valve element 26 and the shaft retaining member 90. Accordingly,the whole retaining surface 91 presses the second joint surface 74.Thus, the single shaft 15A is clamped with the latch surface 67 and theretaining surface 91 from both the left and right sides. Hence, latchingis surely performed.

The following is a description of unlatching and removing the PC-sidevalve element 26 in a state where the TC-side valve element 25 islatched to the single shaft 15A and placed in the position for closingthe TC opening 13. The rod support member 77 has two internal threads78A and 78B extending therethrough vertically. External threads 83A and83B of maintenance rods 82A and 82B prepared separately are insertedinto the internal threads 78A and 78B, respectively, from above the rodsupport member 77 and engaged with the internal threads 78A and 78B.FIG. 5B shows a state where the thread engagement has proceeded to acertain extent. That is, the distal end 84A of the external thread 83Ahas advanced to abut on the upper end of the forward end portion of therotary latch 66, and the distal end 84B of the external thread 83B hasprojected from the lower end surface of the rod support member 77. Atthis time, step portions of the maintenance rods 82A and 82B at therespective upper ends of the external threads 83A and 83B are locatedsomewhat above the upper end surface of the rod support member 77.

If the thread engagement of the external threads 83A and 83B iscontinued to proceed further from the state shown in FIG. 5B, the distalend 84A of the external thread 83A pushes downward the upper end of theforward end portion of the rotary latch 66, causing the rotary latch 66to rotate clockwise (in a direction opposite to the one direction)against the resilient force of the spring 68 to reach an unlatchposition as shown in FIGS. 6A and 6B. At this time, the step portions ofthe maintenance rods 82A and 82B at the respective upper ends of theexternal threads 83A and 83B are in contact with the upper end surfaceof the rod support member 77 to stop the thread engagement fromproceeding further. The latch surface 67 of the rotary latch 66 isseparated from the joint surface 73 of the single shaft 15A, and thepressing of the retaining surface 91 against the second joint surface 74is canceled. Thus, the latch between the latch surface 67 and the jointsurface 73 is undone. If the maintenance rods 82A and 82B are movedupward by a manual operation in the unlatched state, the PC-sidevalve-element 26 is moved together with the maintenance rods 82A and82B. In this way, the PC-side valve element 26 can be removed from thevalve body 10. Thus, the seal 64 of the PC-side valve element 26 canreadily be replaced in a state where the PC-side valve element 26 is outof the valve body 10. The PC-side valve element 26 can be reinstalled byreversing the procedure for removal.

The following is a description of a second example of an arrangement forremoving the PC- or TC-side valve element that is not closed when the PCopening 14 or the TC opening 13 is selectively closed, to replace theseal of the valve element, and for reinstalling the valve element afterthe replacement. The description will be made with reference to FIGS. 7Ato 7C. In the example shown in FIGS. 4A to 6B, the spring 68 is used tourge the rotary latch 66 to press the latch surface 67 against the jointsurface 73 so as to latch the valve element to a predetermined position,and the maintenance rods 82A and 82B are used to undo the latch betweenthe latch surface 67 and the joint surface 73. In the second exampleshown in FIGS. 7A to 7C, not a spring but a latch screw 94 is used tourge the rotary latch 66 to press the latch surface 67 against the jointsurface 73 in order to latch the valve element to a predeterminedposition, and an unlatch screw 93 is used to undo the latch between thelatch surface 67 and the joint surface 73. Further, the rod supportmember 77 in FIGS. 7A to 7C has a shorter lateral width than that of therod support member 77 in FIGS. 4A to 6B. However, it may have the samelateral width as that of the rod support member 77 in FIGS. 4A to 6B. Inthe following description of the arrangement shown in FIGS. 7A to 7C,members common to the first and second examples are denoted by the samereference numerals as those in FIGS. 4A to 6B, and a description ofportions common to the first and second examples will be omitted or madebriefly.

The rotary latch 66 in FIGS. 7A to 7C is pivotably supported by the samemeans as in FIGS. 4A to 6B. The insertion hole 69 of the rotary latch 66is formed at an approximately central position in both the lateral andvertical directions of the rotary latch 66. As shown in FIGS. 7A and 7B,the rotary latch 66 has a predetermined thickness as seen in a top viewand is of an approximately rectangular shape that is laterally oblong asseen in a side view. The latch surface 67 is approximately perpendicularto the top surface of the rotary latch 66. The shaft retaining member 90is provided at the right side of the single shaft 15A. The shaftretaining member 90 extends vertically from the upper end surface to thelower end surface of the PC-side valve element 26. However, thearrangement may be such that the rod support member 77 is extendedrightward, and the shaft retaining member 90 is provided on the PC-sidevalve element 26 at a position below and away from the rod supportmember 77, as in the case of FIGS. 4A to 4C.

The rod support member 77 above the rotary latch 66 is formed with twopairs of insertion holes 97 and 98 and internal threads 95 and 96. Theinsertion hole 97 and the internal thread 95 are vertically adjacent toeach other, and so are the insertion hole 98 and the internal thread 96.The latch screw 94 is engaged with one internal thread 96 for latching.The unlatch screw 93 is engaged with the other internal thread 95 forunlatching. The latch screw 94 is located above the forward end portion(right end portion in FIG. 7B) of the rotary latch 66. The unlatch screw93 is located above the rear end portion (left end portion in FIG. 7B)of the rotary latch 66. The head of the latch screw 94 is formed with acone hexagon socket 88 for engagement. Similarly, the head of theunlatch screw 93 is formed with a cone hexagon socket 87 for engagement.A tool is inserted into the insertion hole 97 and the internal thread 95or into the insertion hole 98 and the internal thread 96, and the tip ofthe tool is engaged with the cone hexagon socket 87 or 88. In thisstate, the tool is turned, thereby allowing the latch screw 94 or theunlatch screw 93 to be rotated to advance or retract.

In the latched state shown in FIGS. 7A and 7B, the latch screw 94 is inan advanced position, and the unlatch screw 93 is in a completelyretracted position. The rotary latch 66 has been pivoted in onedirection. Consequently, the whole of the latch surface 67 of the rotarylatch 66 is pressing the joint surface 73 of the single shaft 15A.Counterforce produced at this time is transmitted to the retainingsurface 91 through the rotary latch 66, the rotating shaft 70, thePC-side valve element 26 and the shaft retaining member 90. Accordingly,the whole retaining surface 91 presses the second joint surface 74.Thus, the single shaft 15A is clamped with the latch surface 67 and theretaining surface 91 from both the left and right sides. Hence, latchingis surely performed.

If the latch screw 94 is retracted while the unlatch screw 93 isadvanced in the latched state shown in FIGS. 7A and 7B, the rotary latch66 is pivoted counterclockwise (in a direction opposite to the onedirection) to reach an unlatched state as shown in FIG. 7C, in which thelatch surface 67 is separate from the joint surface 73 of the singleshaft 15A. It should be noted that the inner diameters of the insertionholes 97 and 98 are smaller than the outer diameters of the unlatchscrew 93 and the latch screw 94. Therefore, there is no possibility ofthe screws 93 and 94 falling off the rod support member 77 as a resultof excessively turning them or during an operation. In a state where thevalve element is unlatched, the tip of a hooking tool is engaged withthe lower side of the rod support member 77 or the rotary latch 66, andthe hooking tool is moved upward, whereby the PC-side valve element 26can be removed from the valve body 10. The seal 64 of the PC-side valveelement 26 can readily be replaced in a state where the PC-side valveelement 26 is out of the valve body 10. The PC-side valve element 26 canbe reinstalled by reversing the procedure for removal.

It should be noted that the present invention is not necessarily limitedto the foregoing embodiments but can be modified in a variety of wayswithout departing from the gist of the present invention.

1. A gate valve including: a valve body having a transfer chamberopening and a process chamber opening formed in mutually opposing wallsthereof, respectively; and a transfer chamber-side valve element and aprocess chamber-side valve element provided in said valve body, saidtransfer chamber-side valve element and process chamber-side valveelement being connected to a single shaft; wherein said transferchamber-side valve element and said process chamber-side valve elementare controlled by actuation of said single shaft so that said transferchamber-side valve element closes said transfer chamber opening, or saidprocess chamber-side valve element closes said process chamber opening,or both said transfer chamber-side valve element and said processchamber-side valve element fully open said transfer chamber opening andsaid process chamber opening, respectively, to allow an object to passthere through; said gate valve comprising; a rotary latch pivotablysupported on an inner surface of at least one of said processchamber-side valve element and said transfer chamber-side valve element,said rotary latch having a latch surface at a forward end thereof;wherein when a rotational force is applied to said rotary latch in onedirection, said latch surface is pressed against a joint surface of saidsingle shaft, whereby said at least one of said process chamber-sidevalve element and said transfer chamber-side valve element is latched tosaid single shaft, and when a rotational force is applied to said rotarylatch in a direction opposite to said one direction, said latch surfaceis separated from said joint surface of said single shaft to unlatchsaid at least one of said process chamber-side valve element and saidtransfer chamber-side valve element.
 2. A gate valve according to claim1, further comprising: a rod support member provided on the innersurface of said at least one of said process chamber-side valve elementand said transfer chamber-side valve element at a position above saidrotary latch, said rod support member having an internal thread; aspring interposed between said rod support member and a rear end portionof said rotary latch; and a maintenance rod having an external thread,said external thread being engaged with said internal thread of said rodsupport member; wherein a rotational force is applied to said rotarylatch in said one direction by resilient force of said spring, and arotational force is applied to said rotary latch in the directionopposite to said one direction by advance of a distal end of saidexternal thread of said maintenance rod.
 3. A gate valve according toclaim 1 or 2, wherein the latch surface of said rotary latch and thejoint surface of said single shaft are slant surfaces as seen in a topview, wherein whole of the slant latch surface is joinable to the slantjoint surface.
 4. A gate valve according to claim 1 or 2, furthercomprising; a shaft retaining member formed on the inner surface of saidat least one of said process chamber-side valve element and saidtransfer chamber-side valve element, said shaft retaining member havinga retaining surface formed at a distal end thereof; and a second jointsurface formed on a side of said single shaft laterally opposite to saidjoint surface; wherein the retaining surface of said shaft retainingmember and the second joint surface of said single shaft are slantsurfaces as seen in a top view, wherein whole of the slant retainingsurface is joinable to the slant second joint surface.
 5. A gate valveaccording to claim 1, further comprising: a rod support member providedabove said rotary latch; a latch screw provided on said rod supportmember at a position above one of forward and rear end portions of saidrotary latch; and an unlatch screw provided on said rod support memberat a position above the other of the forward and rear end portions ofsaid rotary latch; wherein a rotational force is applied to said rotarylatch in one direction by advance of said latch screw and retraction ofsaid unlatch screw, and a rotational force is applied to said rotarylatch in a direction opposite to said one direction by retraction ofsaid latch screw and advance of said unlatch screw.
 6. A gate valveaccording to claim 5, wherein said rod support member is formed with twopairs of insertion holes and internal threads that are verticallyadjacent to each other, respectively, said latch screw being engagedwith one of said internal threads, said unlatch screw being engaged withthe other of said internal threads, wherein said latch screw and saidunlatch screw have respective grooves for engagement formed on theirheads, so that said latch screw and said unlatch screw are rotatablewith a tool by engaging its tip with said groove of each screw.
 7. Agate valve according to claim 5 or 6, wherein the latch surface of saidrotary latch and the joint surface of said single shaft are slantsurfaces as seen in a top view, wherein whole of the slant latch surfaceis joinable to the slant joint surface.
 8. A gate valve according toclaim 5 or 6, further comprising: a shaft retaining member formed on theinner surface of said at least one of said process chamber-side valveelement and said transfer chamber-side valve element, said shaftretaining member having a retaining surface formed at a distal endthereof; and a second joint surface formed on a side of said singleshaft laterally opposite to said joint surface; wherein the retainingsurface of said shaft retaining member and the second joint surface ofsaid single shaft are slant surfaces as seen in a top view, whereinwhole of the slant retaining surface is joinable to the slant secondjoint surface.